Step 1: Use the hydrostatic pressure relation.
The pressure difference measured by a U-tube manometer is
\[
\Delta P=\rho gh.
\]
Given,
\[
\rho=13600\ \mathrm{kg/m^3},
\]
\[
g=9.81\ \mathrm{m/s^2},
\]
\[
h=10\ \mathrm{cm}=0.1\ \mathrm{m}.
\]
Step 2: Calculate the pressure difference.
\[
\Delta P
=
13600\times9.81\times0.1
=
13341.6\ \mathrm{Pa}
\]
\[
=13.34\ \mathrm{kPa}.
\]
Hence,
\[
\boxed{13.34\ \mathrm{kPa}}
\]
Therefore,
\[
\boxed{(C)}
\]
is the correct answer.